Type 2 Diabetes (T2D) is a major health priority within the VA. More than 24% of Veterans have T2D, twice the national average. There is an increasing population of female veterans in the VA in the premenopausal age range. Premenopausal women with T2D have poorer health-related outcomes compared with age-matched men with T2D. The mechanisms for this sex difference in T2D are unknown. Aerobic power predicts the incidence of the poor health-related outcomes associated with T2D. T2D negatively impacts aerobic power to a greater degree in premenopausal women with T2D compared with men with T2D. Aerobic power is partially dependent on skeletal muscle bioenergetics. This proposal is designed to address a clinically significant knowledge gap related to women with T2D, to identify potential targets for clinical therapies to improve the health of women with T2D, and to provide training in several specific methods that will prepare me for a successful transition to independence. Aerobic power is partially dependent on skeletal muscle bioenergetics: signaling associated with and measures of cellular energy balance and mitochondrial biogenesis/function. Estrogen (E2) signaling is reported to be supportive of skeletal muscle bioenergetics, however, my surprising preclinical data suggest that the physiological context in which estrogen signaling is studied is important. My pilot data reveal an unexpected adverse interaction of E2 and diabetes on the regulators of skeletal muscle bioenergetics. My working hypothesis is that diabetes suppresses E2-mediated support of bioenergetics in skeletal muscle of reproductive aged female rats. I will address this hypothesis with two specific aims: Aim 1: To test the impact of the diabetic environment on skeletal muscle E2 signaling and mitochondrial biogenesis in vitro. This aim will determine impact of diabetes on E2-mediated support of signaling associated with and measures of cellular energy balance and mitochondrial biogenesis. Through intricate signaling studies data will be generated to identify the diabetes-associated mechanism(s) that could be targeted to restore mitochondrial bioenergetics in women with T2D. Aim 2: To understand whether the disruption of E2 support of skeletal muscle bioenergetics in vivo by diabetes impairs exercise capacity. This aim will determine the bioenergetic consequences of the diabetes-associated disruption of E2 support of skeletal muscle through measures of substrate utilization, mitochondrial function, and aerobic exercise capacity. This proposal addresses the clinically relevant knowledge gap related to decreased functional status of premenopausal women with T2D and could identify potential targets for clinical therapies to improve the health of women with T2D. Through training with my mentors, coursework, and the successful completion of the project specific aims, I will further develop my knowledge base and skillset in primary cell culture, cellular signal transduction, and manipulation of E2 and derive new data that will set me on the path to achieve my overall goal of becoming a successful, independent VA scientist.